1. Field of the Invention
The present invention relates to methods of inertial welding. More specifically, the present invention relates to inertial welding methods for attaching a conical component to a side of a pipe or tube.
2. Description of Related Art
Friction welding is a technology used to join metal or other thermoplastic components using heat generated by friction between the components. This technology is often used to join a tube, solid rod, or other symmetrical object to another component. Generally, the needed friction between the parts is obtained by rotating one part and pressing it against the other, which is held stationary. The heat generated by the resulting friction softens the material of the parts, and the softened materials may then be forced together and allowed to become rigid, thus forming a stable weld.
This general method is commonly used to weld a tube or pole to a flat surface, to weld two poles or tubes end-to-end, and to create butt joints. In friction welding, the part being rotated is generally substantially symmetrical, and is rotated about its axis of symmetry. This provides stability during the rotation of the part. In addition, the face of the part being rotated and the receiving face of the other part are generally flat, planar surfaces such that when placed in contact, there is a constant interface between the rotating part and the surface to which it is being joined. The part being rotated may be solid, such as a metallic rod, or may be hollow, such as a metal pipe or tube. Both of these configurations yield a stable rotation and a constant interface between the rotating part and the weld surface.
The non-rotating part to which the substantially symmetrical component is being welded may also be symmetrical, as when two rods or tubes are being joined end-to-end. Alternatively, the components may be asymmetrical. For example, the receiving component may simply include a flat surface to which a rotatable component is to be joined. Alternatively, the receiving component may include an aperture against which the rotatable part is pressed. In most applications, it is important that the surface of the receiving component be relatively flat, and thus be conducive to being aligned substantially parallel to the surface of the part to be welded. This further helps to provide a constant interface between the rotating part and the receiving part, thus encouraging the formation of a secure weld.
Mathematical models have been generated which are used to determine the rotational speed which must be imparted to the rotatable member and the pressure with which it must be pushed against the stationary component in order to generate sufficient heat to yield a proper weld. These models have been produced for a variety of welding applications and situations. In some friction welding methods, the rotatable component is rotated using a motorized assembly to provide a predetermined velocity and pressure. In other friction welding methods, the rotatable part is coupled to a flywheel of a predetermined size which is brought up to a specified velocity and pressed against the stationary piece at a predetermined pressure. This family of methods is referred to as inertial welding. Both methods operate using substantially the same principles.
In these methods, the parts to be welded are first aligned such that the surfaces to be joined are substantially parallel. The part to be rotated is then rotated at a specific speed and pressed against the opposite surface with a predetermined pressure. The contact and rotation of the parts generates sufficient heat to render plastic the material of the parts at their interface. As the material of the stationary and rotating components begins to become plastic, the rotation of the parts sweeps outward some of the material at the interface of the two components. This action helps to compensate for a less-than optimal interface by removing detrimental surface features. It also rids the interface of oxidized materials or impurities that could weaken the weld. The material driven from the interface builds up and cools about the weld, forming a structure called a “weld flash” about the interface of the two components. The weld flash is desirably uniformly distributed about the joint, and provides a smooth, aesthetically-acceptable surface at the weld.
The relatively flexible parameters of friction welding and the aesthetic results of the process have made frictional welding a popular and useful technique for joining metal components. As briefly noted above, however, this technique has largely found successful use in applications requiring the creation of butt joints, the coaxial fusion of tubes or poles, and the fusion of a tube or pole to a flat surface. Some designs call for the fusion of two tubular objects oriented substantially perpendicularly such that a first tubular object is to be fused into the rounded side surface of the other tubular object. One example of this is applications requiring the attachment of a tube into the side of another tube to form a T-joint. This type of weld is incompatible with existing friction welding methods since the attachment face of the receiving part is not planar, resulting in uneven contact, heating, and plasticity.
As a result, objects requiring such construction must be assembled using alternate casting or machining methods which are generally expensive and which may add production time and difficulty to the creation of the object. These alternative methods may further result in a product having a longer production time, higher cost, and more complex design.